fix: resolve Gemini CLI 0.37.0 session capture failures (#1664) (#1692)

Three root causes prevented Gemini sessions from persisting prompts,
observations, and summaries:

1. BeforeAgent was mapped to user-message (display-only) instead of
   session-init (which initialises the session and starts the SDK agent).

2. The transcript parser expected Claude Code JSONL (type: "assistant")
   but Gemini CLI 0.37.0 writes a JSON document with a messages array
   where assistant entries carry type: "gemini". extractLastMessage now
   detects the format and routes to the correct parser, preserving
   full backward compatibility with Claude Code JSONL transcripts.

3. The summarize handler omitted platformSource from the
   /api/sessions/summarize request body, causing sessions to be recorded
   without the gemini-cli source tag.

Co-authored-by: Claude <noreply@anthropic.com>

src/cli/adapters/gemini-cli.ts

@@ -13,7 +13,7 @@ import type { PlatformAdapter } from '../types.js';
  *   Notification  → observation (system events like ToolPermission)
  *
  * Agent:
- *   BeforeAgent   → user-message (captures user prompt)
+ *   BeforeAgent   → session-init (initializes session, captures user prompt)
  *   AfterAgent    → observation  (full agent response)
  *
  * Tool:

src/cli/handlers/summarize.ts

@@ -18,6 +18,7 @@ import { ensureWorkerRunning, workerHttpRequest } from '../../shared/worker-util
 import { logger } from '../../utils/logger.js';
 import { extractLastMessage } from '../../shared/transcript-parser.js';
 import { HOOK_EXIT_CODES, HOOK_TIMEOUTS, getTimeout } from '../../shared/hook-constants.js';
+import { normalizePlatformSource } from '../../shared/platform-source.js';
 
 const SUMMARIZE_TIMEOUT_MS = getTimeout(HOOK_TIMEOUTS.DEFAULT);
 const POLL_INTERVAL_MS = 500;
@@ -66,13 +67,16 @@ export const summarizeHandler: EventHandler = {
       hasLastAssistantMessage: !!lastAssistantMessage
     });
 
+    const platformSource = normalizePlatformSource(input.platform);
+
     // 1. Queue summarize request — worker returns immediately with { status: 'queued' }
     const response = await workerHttpRequest('/api/sessions/summarize', {
       method: 'POST',
       headers: { 'Content-Type': 'application/json' },
       body: JSON.stringify({
         contentSessionId: sessionId,
-        last_assistant_message: lastAssistantMessage
+        last_assistant_message: lastAssistantMessage,
+        platformSource
       }),
       timeoutMs: SUMMARIZE_TIMEOUT_MS
     });